linear equation with one variable..confusing!

[biker317]

Car salesperson M's compensation for any week is $420 plus 5 percent of M's total sales above $1,000 for that week. Salesperson N earns 7 percent of N's total sales for that week. If the salespeople earn the same compensation for a given week, what is the value of each salesperson's total sales for the week?

(A) $21,000
(B) $18,500
(C) $17,000
(D) $6,000
(E) $3,500




The correct answer is B
Please give this a shot

[Brent@GMATPrepNow]

Car salesperson M's compensation for any week is $420 plus 5 percent of M's total sales above $1,000 for that week. Salesperson N earns 7 percent of N's total sales for that week. If the salespeople earn the same compensation for a given week, what is the value of each salesperson's total sales for the week?
(A) $21,000
(B) $18,500
(C) $17,000
(D) $6,000
(E) $3,500
The correct answer is B
Please give this a shot

There's a piece missing here. We need something that says that the two salespeople had the same total sales for the week. The part in the question that says "what is the value of each salesperson's total sales for the week?" seems to imply that the two people had the same sales totals for the week.

If it is the case that they both had the same sales for the week, we can solve this as follows:
Let X = M's total sales for the week, which means X = N's total sales for the week

M's compensation for the week = 420 + 0.05(X-1000)
(Notice that X-1000 will equal the total sales above $1,000 for that week)
N's compensation for the week = 0.07X
If they both get paid the same then we can write the equation:
420 + 0.05(X-1000) = 0.07X
Solve for X to get X=18,500 (B)

[biker317]

thanks Brent, I had the same opinion too, I was just making sure that I wasnt missing something..FYI this is a knewton question for their practise test